O-290 Oil P problem

[wolf.]

I have a Long with a O-290,

since a while every now and then the Oil P drops to zero or below 10psi then comes up again and so forth, if the engine is running for 20 min or more it happens less frequently. I have the non adjustable cage type relief valve. I cleaned the valve replaced the sphere and the spring and it worked for 3h flight now it does it again. Any ideas what the problem could be?? (zero Oil P makes me somehow nervous in flight)

 

wolf.

[Drew Swenson]

try a different gauge hooked directly to your engine to verify whether it is the engine, gauge, or wiring.

[Kent Ashton]

The first thing to suspect is the sender, especially the electrical ground to the sender. And senders themselves are fragile--there is a little arm in there rubbing on a coil of copper wire.

 

I think an O-290 is like an O-320. The oil pressure system is so simple in these engines that there is almost no way you can have real zero oil pressure without some sort of massive leak/catestrophic failure.

 

I had high oil pressure readings once. After days of fretting over it, it was the sender.

-Kent

[wolf.]

I have had the same problem with a completely different set up. I had an old sender and a westach instrument, now I have a new sender and an EFIS. But I'lll still try changing the sender.

 

wolf.

[dirtdox]

I had a oil pressure gauge(automotive) do this. It turned out to be a loose connection at the sending unit.